The present invention relates generally to a barrel assembly for an axial piston pump, and more particularly to a barrel having a ring shaped cavity closed to a central bore at least in part by a collar and a method of forming the same.
Currently, barrels for axial piston pumps are usually made from castings. Such a casting is illustrated in U.S. Pat. No. 6,035,828, entitled Hydraulically-Actuated System Having A Variable Delivery Fixed Displacement Pump, which issued to Anderson et al. on Mar. 14, 2000. However, this method of production, while adequate, can be undesirable for a number of reasons. For instance, this method of producing pump barrels can result in long production times and difficulty in producing accurate parts. First, forming the casting can be difficult because the core that creates a ring shaped accumulator cavity defined by the barrel can shift position during pouring of the casting. This can cause positional tolerances of the barrel to be exceeded. In addition, when the cast material is not homogenous in content, it will contain relatively hard granules that are separated by relatively soft material. As the relative hardness of the casting granules approaches the hardness of the machining tool, the machining tool can be worn excessively fast.
The present invention is directed to overcome a one or more of the problems as set forth above.
According to one aspect of the present invention, a barrel assembly for an axial piston pump includes a barrel that defines a ring shaped cavity which opens to a central bore, and a plurality of parallel piston bores that surround the central bore and open to the ring shaped cavity. A collar is attached to the barrel and closes the ring shaped cavity to the central bore.
According to another aspect of the present invention, a pump includes a housing. A barrel assembly is mounted in the housing and provides a collar that is attached to the barrel to define a ring shaped cavity which surrounds, but is closed to, a central bore. The barrel defines a plurality of parallel piston bores that open to the ring shaped cavity. A piston is slideably received in each of the piston bores. A drive plate which has a slanted drive surface is rotateably mounted in the housing and is operably coupled to each piston.
According to yet another aspect of the present invention, a method of making a barrel assembly for a pump includes forming a barrel to provide a ring shaped cavity that opens to a central bore. The ring shaped cavity is closed to the central bore at least in part by attaching a plug into the barrel.